This invention relates to an automatic cutoff and tester apparatus of gas supply and more particularly to an automatic cutoff and tester apparatus of gas supply having diaphragm powered valve which is operated by sensor means in accordance with swing over a predetermined amplitude of earthquake, etc. The diaphragm powered valve is disposed within a chamber which has an opening on a gas pipe wall and is formed by extended cylindrical wall of the gas pipe.
The valve automatically closes an outlet of the opening in accordance with operation of the diaphragm which is operated by a press lever assembly arranged to a sensor means.